Joining structure for an acrylic rubber composition and heat-resistant hose

ABSTRACT

An acrylic rubber composition in which the base material is an acrylic rubber comprising monomer units of ethyl acrylate, n-butyl acrylate, and cure site monomer, with a ratio (B/A) of the amount of n-butyl acrylate (B) with respect to ethyl acrylate (A) of 1.0 or less by weight. A heat-resistant hose having a layer of this acrylic rubber composition as the innermost layer. The above constitution of the invention provides the acrylic rubber composition effective for preventing aluminum fixing while retaining the material properties of acrylic rubber and its excellent characteristics. The present invention also provides a heat-resistant hose using this acrylic rubber composition at the surface which is to be fitted with an aluminum member.

TECHNICAL FIELD

The present invention relates to an acrylic rubber composition and aheat-resistant hose. More particularly, the present invention relates toan acrylic rubber composition with sufficient heat resistance,compression set resistance, oil resistance, and the like. When used as aheat-resistant hose, this acrylic rubber composition prevents fixing toa member made of aluminum. In addition, the acrylic rubber compositionof the present invention can favorably extrude a large diameter hose. Inaddition, the present invention relates to a heat-resistant hose usingthe same.

BACKGROUND ART

In the prior art, rubber compositions having a base material of acrylicrubber are often used in hoses that require heat resistance, oilresistance, and cold resistance, such as in oil system hoses or airsystem hoses and the like for automobiles. In general, acrylic rubberhas good heat resistance and oil resistance and also has goodcompression set resistance. As a result, when used in hoses, it hasexcellent sealing quality at the hose connection part.

When an acrylic rubber composition is used in a heat-resistant hose thatis used under extreme conditions, such as in an air hose for asupercharger in a turbocharger assembly vehicle, if the connecting pipeis made of aluminum (or its alloy), the acrylic rubber composition oftenbecomes fixed to the aluminum. The replacement operation of theheat-resistant hose has therefore been difficult (henceforth “aluminumfixing” refers to this fixing phenomenon).

The reason for the above aluminum fixing problem is thought to be thefollowing. Aluminum is readily oxidized by the oxygen in the air to formalumina. Further, in the presence of water, alumina readily forms ahydroxide. This hydroxide and the rubber material react, which causesaluminum fixing.

In the prior art, in order to prevent aluminum fixing, in the inventiondescribed in Japanese Laid-Open Patent Publication Number 2001-2877 forexample, an acryl-silicon copolymer is added to the acrylic rubber. Inthe invention described in Japanese Laid Open Patent Publication NumberH6-88005, a phosphate ester plasticizer is added to the acrylic rubber,or a fatty acid processing aid or a metal soap compound is mixed intothe acrylic rubber. Furthermore, in the invention described in JapaneseLaid Open Patent Publication Number H5-148476, by adding a siliconprocessing aid, there is an effect of surface covering.

However, with the prior art described above, apart from theireffectiveness in preventing aluminum fixing, the above strategies resultin normal state physical properties which are inferior for acrylicrubber. In addition, there can be reduced heat resistance andcompression set resistance which are characteristics of the acrylicrubber, or there may be bleeding of the mixing agents.

An object of the present invention is to provide an acrylic rubbercomposition which effectively prevents aluminum fixing while stillretaining the physical properties and superior characteristics ofacrylic rubber. A further object of the present invention is to providea heat-resistant hose which uses this acrylic rubber composition insurfaces that join with aluminum or aluminum alloy members.

DISCLOSURE OF THE INVENTION

A first aspect of the invention is an acrylic rubber composition for usein a heat-resistant hose which joins with a member made of aluminum oraluminum alloy, said acrylic rubber composition being used in a layerwhich constitutes a joining surface with said member, comprising:acrylic rubber as a base material comprising monomer units of ethylacrylate (A), n-butyl acrylate (B), and a cure site monomer; and a ratio(B/A) of the amount of n-butyl acrylate with respect to ethyl acrylateof 1.0 or less.

With the acrylic rubber composition of the first aspect of theinvention, because the base material of acrylic rubber contains monomerunits of ethyl acrylate, n-butyl acrylate, and cure site monomers, andparticularly because it contains n-butyl acrylate, the excellentcharacteristics of acrylic rubber of heat resistance, oil resistance,compression set resistance, and the like are retained.

Ethyl acrylate, which has a smaller electron donating property(polarization of charge within the molecule) than n-butyl acrylate, hasa smaller reactivity with aluminum hydroxide, and aluminum fixing isless likely to occur. With the acrylic rubber used in the acrylic rubbercomposition of invention 1, B/A is 1.0 or less, or in other words, thereis an equal or greater amount of ethyl acrylate as compared with theamount of n-butyl acrylate. As a result, aluminum fixing is effectivelysuppressed.

In addition, with the acrylic rubber composition of the first aspect ofthe invention, because silicon mixing agents, or phosphate esterplasticizers, fatty acid processing aids, metal soap compounds and thelike are not mixed in as in the prior art, the problems of theirbleeding do not occur. In addition, the excellent properties of acrylicrubber of heat resistance, oil resistance, compression set resistance,and the like are retained.

A second aspect of the present invention is an acrylic rubbercomposition relating to the first aspect of the invention, wherein: theratio of amount B/A is 0.1-1.0.

When the ratio (B/A) of the amount of n-butyl acrylate (B) with respectto ethyl acrylate (A) is within the range of 0.1-1.0, the effect of thefirst aspect of the invention is particularly apparent.

When B/A exceeds 1.0, because there is excess n-butyl acrylate in themonomer composition of the acrylic rubber, aluminum fixing of theacrylic rubber composition occurs more readily. When B/A is less than0.1, because there is an insufficient absolute amount of n-butylacrylate in the monomer composition of acrylic rubber, the excellentproperties of acrylic rubber of heat resistance, oil resistance,compression set resistance, and the like may be compromised.

A third aspect of the present invention is an acrylic rubbercomposition, relating to the first and second aspects of the invention,wherein: the amount of cure site monomer in the acrylic rubber is 0.5 -2% by weight.

The amount of cure site monomer in the acrylic rubber which is the basematerial of the acrylic rubber composition is not restricted, but it ispreferably 0.5 - 2% by weight in the acrylic rubber.

When the amount of cure site monomer is less than 0.5% by weight, theremay be inadequate vulcanization of the acrylic rubber, and the stickingproperty increases. In addition, there is the risk of heat fixing of therubber composition to aluminum. On the other hand, because cure sitemonomers have a larger electron donating property compared to ethylacrylate and n-butyl acrylate, when the amount exceeds 2% by weight,after vulcanization, the excess cure group may result in aluminum fixingof the acrylic rubber composition.

A fourth aspect of the present invention is a heat-resistant hose, beinga heat-resistant hose which joins with a member made of aluminum oraluminum alloy, wherein: an acrylic rubber composition of one of thefirst to third aspects of the invention is used in a layer whichconstitutes a joining surface with the member.

With the heat-resistant hose of the fourth aspect of the invention,because an acrylic rubber composition of the first to third aspects ofthe invention is used in a layer which constitutes the joining surfacewith an aluminum or aluminum alloy member, aluminum fixing of theheat-resistant hose is effectively prevented. At the same time, the heatresistance, oil resistance, compression set resistance, and the like ofthe hose is maintained.

A fifth aspect of the present invention is a heat-resistant hoserelating to the heat-resistant hose of the fourth aspect of theinvention, wherein: the heat-resistant hose is used as a highheat-resistant hose in an air system or oil system of an automobile.

Although the purpose of the heat-resistant hose of the fourth aspect ofthe invention is not restricted, from the actions and advantages of thefourth aspect of the invention, this is ideally suited for use in highheat-resistant hose of air systems or oil systems of automobiles.

BEST MODES OF CARRYING OUT THE INVENTION

[Acrylic Rubber Composition]

The acrylic rubber composition of the present invention is a rubbercomposition used in a heat-resistant hose which joins with a member madeof aluminum or aluminum alloy and is used in a layer which constitutes ajoining surface with this member.

The type of aluminum or aluminum alloy member is not limited, but arepresentative example is a hose connecting pipe for use inturbochargers in automobiles. Other examples also include intercoolerand intake manifold, and the like.

The acrylic rubber used as the base material for the acrylic rubbercomposition is one which is copolymerized by any of the known methods,such as emulsion polymerization, suspension polymerization, solutionpolymerization, bulk polymerization, and the like. The monomercomponents for the acrylic rubber include at least ethyl acrylate,n-butyl acrylate, and cure site monomer. The ratio B/A of the amount ofn-butyl acrylate (B) to the amount of ethyl acrylate (A) is 1.0 or less,preferably in the range of 0.1-1.0.

The acrylic rubber which is the base material for the acrylic rubbercomposition can also include suitable monomer components other thanthose described above. Examples of suitable monomer components includecompounds containing a carboxyl group such as acrylic acid, methacrylicacid, crotonic acid, 2-pentenoic acid, maleic acid, fumaric acid,itaconic acid, and the like.

Other examples of monomer components include acrylic esters containingfluorine, such as 1,1-dihydroperfluoroethyl(meta)acrylate,1,1-dihydroperfluoropropyl(meta)acrylate,1.1,5-trihydroperfluorohexyl(meta)acrylate,1,1,2,2-tetrahydroperfluoropropyl(meta)acrylate,1,1,7-trihydroperfluoroheptyl(meta)acrylate,1,1-dihydroperfluorooctyl(meta)acrylate,1,1-dihydroperfluorodecyl(meta)acrylate, and the like.

Other examples include acrylic esters containing a hydroxyl group, suchas 1-hydroxypropyl(meta)acrylate, 2-hydroxypropyl(meta)acrylate,hydroxyethyl(meta)acrylate, and the like.

Other examples also include acrylic esters containing a tertiary aminogroup such as diethylaminoethyl(meta)acrylate,dibutylaminoethyl(meta)acrylate, and the like; methacrylates such asmethyl methacrylate, octyl methacrylate, and the like; alkylvinylketones such as methylvinyl ketone, and the like; vinyl and allyl etherssuch as vinylethyl ether, allylmethyl ether, and the like; vinylaromatic compounds such as styrene, alpha-methylstyrene, chlorostyrene,vinyltoluene, and the like; vinyl nitriles such as acrylonitrile,methacrylonitrile, and the like. Other examples also include ethylene,propylene, vinyl chloride, vinylidene chloride, vinyl fluoride,vinylidene fluoride, vinyl acetate, vinyl propionate, alkyl fumarate,and the like.

The type of cure site monomer is not limited. They can be selected forexample from cure site monomers containing carboxyl group, cure sitemonomers containing epoxy group, cure site monomers containing activatedchlorine group, and the like. Examples of the aforementioned cure sitemonomer containing carboxyl group include monoalkyl ester maleate,monoalkyl ester fumarate, monoalkylester itaconate, and the like. Theamount of cure site monomer in the acrylic rubber is not limited, butpreferably it is 0.5-2% by weight.

In the acrylic rubber composition of the present invention, as long asthe effect of the invention is not inhibited, other suitable mixingcomponents can be added as needed. These mixing components include avulcanizing agent, carbon black, antioxidant, plasticizer, processingaid, scorch retarder, flame retardant, coloring agent, and the like.

The type or amount of the aforementioned vulcanizing agent is notlimited, but in an acrylic rubber that contains carboxyl group, avulcanizing agent, comprising a diamine compound, non-chelatingguanidine compound and metal chelated guanidine compound, is mixed at4.3- 8.1 parts by weight with respect to 100 parts by weight of acrylicrubber.

For the aforementioned carbon black, it preferably has an average grainsize of 30-60 nm with a DBP oil absorption amount of 150 cc/100 g orgreater. The mixing amount is preferably around 50- 80 parts by weightwith respect to 100 parts by weight of acrylic rubber.

[Heat-Resistant Hose]

The heat-resistant hose of the present invention is connected to analuminum or aluminum alloy member. The heat-resistant hose of thepresent invention uses one of the aforementioned acrylic rubbercompositions in a layer which constitutes a joining surface with thismember.

The usage of the heat-resistant hose is not limited, but preferably, itis used in high heat-resistant hose in air systems or oil systems ofautomobiles. An example of a high heat-resistant hose of an air systemincludes a hose for use in a supercharger and the like. Examples of highheat-resistant hoses for an oil system include engine oil cooler hose,AT (automatic transmission) oil cooler hose, power steering hose, andthe like.

The constitution of the rubber hose can be, for example, a single layerhose having a single rubber layer of the aforementioned acrylic rubbercomposition. Depending on the purpose of the hose, it can be amulti-layer hose, having in addition to the rubber layer of theaforementioned acrylic rubber composition, a middle layer or outer layerof a rubber layer which uses acrylic rubber or a rubber other thanacrylic rubber (for example, fluororubber, fluorine modified rubber,hydrine rubber, CSM, CR, NBR, ethylene-propylene rubber, and the like).In addition, a reinforcement layer using reinforcement fibers or wirescan be provided in the middle layer or outermost layer. In either case,with multi-layer hoses, the aforementioned acrylic rubber compositionlayer constitutes the innermost layer of the hose.

Embodiment

[Preparation of Acrylic Rubber Non-Vulcanized Composition]

Acrylic rubber compositions of Examples 1-6 and Comparative examples 1-4shown in Tables 1, 2, and 3 were prepared.

With regard to the acrylic rubber compositions of each example, in therow labeled “Acrylic polymer” in Tables 1 and 2, the monomer compositionof the acrylic rubber including the type and amount of cure site monomeris shown. The row labeled “Ethyl acrylate/n-butyl acrylate” shows themixing ratio of ethyl acrylate and n-butyl acrylate.

In addition, in Table 3, the basic mixture for the acrylic rubbercompositions of the examples are shown. The numerical values of Table 3have units of phr (parts per hundred parts of rubber). The names of theproducts that were actually used as the mixture components in Tables 1-3are listed in Table 4.

Non-vulcanized acrylic rubber having the monomer compositions ofExamples 1-6 and Comparative examples 1-4 were prepared. All of theingredients except for the vulcanizing agent were kneaded with a 1.7 Lbanbury mixer. Furthermore, in an 8 inch roll, the vulcanizing agent wasadded, and the acrylic rubber non-vulcanized composition for each of theexamples were prepared.

[Evaluation of the Acrylic Rubber Non-Vulcanized Composition]

(Normal State Physical Properties)

Using the acrylic rubber non-vulcanized composition for each example, anon-vulcanized rubber sheet of thickness 2 mm was made with an 8 inchmixing roll. After press vulcanization at 160 degrees C.×60 minutes,this was oven vulcanized at 150 degrees C.×8 hours. A rubber test sheetfor evaluating normal state physical properties was obtained. For eachof the rubber test pieces, the tensile strength (MPa), elongation atbreak (%), and tear strength (B method, N/mm) were evaluated accordingto JIS K 6251. The evaluation results are shown in the row “Normal StatePhysical Properties” in Tables 1 and 2.

(Heat Resistance)

Using the acrylic rubber non-vulcanized composition for each example,rubber test sheets were made in the same manner as described above foruse in heat resistance evaluation. After heat aging at 200 degreesC.×168 hours, the tensile strength (MPa), elongation at break (%), andtear strength (B method, N/mm) were evaluated according to JIS K 6257.In addition, a JIS number 5 dumbbell after heat aging was bent 180°, andthe appearance was evaluated for cracks or breakages and the like. Theevaluation results are shown in the row labeled “Heat resistance” inTables 1 and 2. With regard to the bending test, examples in which therewas no damage was evaluated as “OK” and if there was damage, this wasdescribed in concrete terms.

(Compression Set Resistance)

Using the acrylic rubber non-vulcanized composition for each example, alarge test piece was created by press vulcanizing at 160 degrees C.×60minutes and oven vulcanizing at 150 degrees C.×8 hours according to JISK 6262. The compression set resistance (%) after heat aging at 200degrees C.×22 hours was evaluated according to JIS K 6262. Theevaluation results are shown in the row labeled “Compression setresistance” in Tables 1 and 2.

(Low Temperature Properties)

Using the acrylic rubber non-vulcanized composition for each example,rubber test sheets for evaluation of low temperature properties werecreated by the same method as in the aforementioned “Normal StateProperties” section. The low temperature properties for these testpieces were evaluated by the brittle point temperature (degrees C.)according to JIS K 6301. The evaluation results are shown in the rowlabeled “Low temperature properties” in Tables 1 and 2.

(Oil Resistance)

Using the acrylic rubber non-vulcanized composition for each example,rubber test sheets for evaluation of oil resistance were created by thesame method as in the aforementioned “Normal State Properties” section.These test pieces were immersed in IRM 903 oil at 150 degrees C. for 72hours. Afterwards, the oil resistance was evaluated by measuring thevolume change (%). The evaluation results are shown in the row labeled“Oil resistance” in Tables 1 and 2.

(Fixing Property)

Using the acrylic rubber non-vulcanized composition for each example, alarge size test piece (diameter 29 mm, thickness 12.5 mm) was created bypress vulcanizing at 160 degrees C.×60 minutes and oven vulcanizing at150 degrees C.×8 hours according to JIS K6262 item 5. For the materialfor use in the fixing evaluation (fixing evaluation material), sheets ofthickness 2 mm with a surface area somewhat larger than the test pieceswere prepared using aluminum material, iron material, and Teflonmaterial.

Next, the aforementioned test pieces were sandwiched between two sheetsof the aforementioned fixing evaluation materials. This was attached toa testing equipment according to JIS K6262 item 5. This was compressedat a constant compression rate of 25%, and this was treated under theheat aging condition of 200 degrees C.×168 hours. After heat aging, thetest piece was removed from the testing equipment while still sandwichedbetween the fixing evaluation materials. The fixing evaluation materialswere removed from the test piece, and the fixing status of both of theirsurfaces was observed. The results are shown in the row “Metal fixingproperty” in Tables 1 and 2 and are divided into “Aluminum”, “Iron”, and“Teflon”. If even one portion of the rubber material of the test piecewas attached to the fixing evaluation material due to fixing, this isindicated as “X”, if there was none attached, it is indicated as “O”.

[Performance Evaluation of the Heat-Resistant Hose]

[Making the Heat-Resistant Hose]

Using the acrylic rubber non-vulcanized composition for each example, aheat-resistant hose having an inner surface rubber layer of thickness 3mm and an outer surface rubber layer of thickness 2 mm and a middlereinforcement layer was made. For these heat-resistant hoses, the innersurface rubber layers were constituted using the acrylic rubbernon-vulcanized composition of each example. The reinforcement layer wasconstituted by braiding with a piece x carrier of 1×32 fibers at abraiding angle of 55 degrees using para-type aromatic polyamidereinforcement fibers. The same material for the inner surface rubberlayer was used for the outer surface rubber layer in each example.

(Evaluation of the Joint After Aging of the Heat-Resistant Hose)

The heat-resistant hoses created using the acrylic rubber non-vulcanizedcompositions for each example as described above were attached toaluminum cast pipes having a straight diameter of 31 mm and bulgingshape according to JASO M101. These were tightened with a tighteningtorque of 3 N·m by a warm gear clamp according to JASO F207.

After heat aging the attached heat-resistant hose at 200 degrees C.×168hours, the warm gear clamp was removed and the pipe was removed. Anyremnants of rubber on the pipe surface was observed. In addition, afterthis observation, the same heat-resistant hose was again attached to thepipe, and the air inside the hose joint interior was pressurized to 200kPa, and the presence or absence of leakage was confirmed. In the rowlabeled “Joint after aging” of Tables 1 and 2, the visual observationresults of any remnants of rubber are indicated in the “Pipe removal”row, and the presence or absence of leakage is shown in the “Reassemblyleak test”.

(Evaluation of Cold Resistance of the Heat-Resistant Hose)

A heat-resistant hose of each example having a length 25 mm was left for5 hours in a −35 degrees C. environment. Immediately after removing fromthis environment, the heat-resistant hose was sandwiched between twoflat plates and was rapidly compressed by these plates so that the innerdiameter of the hose was halved. Any cracks in the heat-resistant hosewas confirmed. The results are shown in the “Cold resistance” row ofTable 1 and 2.

(Compression Breaking Test of the Heat-Resistant Hose)

A heat-resistant hose of each example having a length 25 mm was heataged at 200 degrees C.×168 hours. Immediately afterwards, theheat-resistant hose was sandwiched between two flat plates and wasrapidly compressed by these plates so that the inner diameter of thehose was halved. Any cracks in the heat-resistant hose was observed. Theresults are shown in the row labeled “Compression break” in Tables 1 and2.

Field of Use in Industry

As described above, according to the present invention, an acrylicrubber composition which maintains sufficient heat resistance,compression set resistance, oil resistance and the like while preventingfixing to aluminum members during use as a heat-resistant hose isprovided. Furthermore, this acrylic rubber composition can favorablyextrude a large diameter hose. Therefore, a good heat-resistant hose canbe made using this acrylic rubber composition. TABLE 1 Ex. 1 Ex. 2 Ex. 3Ex. 4 Ex. 5 Ex. 6 Acrylic Composition Ethylene — — — — 10 — polymer (wt%) Ethyl acrylate 99 89.1 74.3 49.5 66.8 74.3 n-Butyl acrylate 0 9.924.7 49.5 22.2 24.7 Ethyl acrylate/n-butyl acrylate 100/0 90/10 75/2550/50 75/25 75/25 Cure site Monoethyl ester fumarate 1 1 1 1 1 — monomerGlycidyl methacrylate — — — — — 1 (wt %) Normal state physical tensilestrength (MPa) 12.2 12.0 11.4 11.2 12.6 11.6 properties Elongation (%)250 240 230 230 250 220 Tearing (B method, N/mm) 27.2 26.8 26.0 24.131.6 25.8 Heat resistance after Tensile strength (MPa) 9.8 9.8 9.6 9.511.1 9.8 200° C. × 168 h Elongation (%) 120 120 110 100 120 110 Bendingtest OK OK OK OK OK OK Tearing (B method, N/mm) 16.1 16.1 15.6 14.4 19.215.5 Compression set (%) 200° C. × 22 h 25 25 24 26 25 51 Lowtemperature Brittle point temperature (° C.) −18 −23 −29 −33 −34 −30properties Oil resistance-IRM Volume change (%) 12 14 19 24 25 18 903,after 150° C. × 72 hours Metal fixing - Visual observation ◯ ◯ ◯ ◯ ◯ ◯Aluminum, after 200° C. × 168 hours Iron, after Visual observation ◯ ◯ ◯◯ ◯ ◯ 200° C. × 168 hours Teflon, after Visual observation ◯ ◯ ◯ ◯ ◯ ◯200° C. × 168 hours Product Joint after pipe removed after heat aging atno damage no damage no damage no damage no damage no damage perfor-aging 200° C. × 168 hours mance Reassembly leak test no damage no damageno damage no damage no damage no damage Cold after cooling at −35° C. ×5 hrs, breakage no damage no damage no damage no damage no damageresistance compression to 1/2 inner diameter Compression after heataging at 200° C. × 168 h, no damage no damage no damage no damage nodamage no damage break compression to 1/2 inner diameter

TABLE 2 Comp Ex. 1 Comp. Ex. 2 Comp. Ex. 3 Comp. ex. 4 AcrylicComposition Ethylene — — — — polymer (wt %) Ethyl acrylate 24.7 0 74.872.8 n-Butyl acrylate 74.3 99 24.9 24.2 Ethyl acrylate/n-Butyl acrylate25/75 0/100 75/25 75/25 Cure site Monoethyl ester fumarate 1 1 0.3 3monomer Glycidyl methacrylate — — — — (wt %) Normal state physicaltensile strength (MPa) 11.0 10.9 7.9 13.0 properties Elongation (%) 220200 360 180 Tearing (B method, N/mm) 21.9 19.6 27.3 19.3 Heat resistanceafter Tensile strength (MPa) 9.5 9.2 4.1 11.3 200° C. × 168 h Elongation(%) 80 60 120 70 Bending test OK Cracks OK Cracks Tearing (B method,N/mm) 13.2 11.9 14.3 6.9 Compression set (%) 200° C. × 22 h 25 26 79 22Low temperature Brittle point temperature (° C.) −36 −42 −30 −28properties Oil resistance-IRM Volume change (%) 32 43 63 17 903, after150° C. × 72 hours Metal fixing - Visual observation X X X X Aluminum,after 200° C. × 168 hours Iron, after Visual observation ◯ ◯ ◯ ◯ 200° C.× 168 hours Teflon, after Visual observation ◯ ◯ ◯ ◯ 200° C. × 168 hoursProduct Joint after pipe removed after heat aging rubber rubber rubberrubber perfor- aging at 200° C. × 168 hours remains remains remainsremains mance Reassembly leak test leakage leakage leakage leakage Coldafter cooling at −35° C. × 5 hrs, no damage no damage no damage nodamage resistance compression to 1/2 inner diameter Compression afterheat aging at 200° C. × 168 h, no damage breakage no damage breakagebreak compression to 1/2 inner diameter

TABLE 3 Number of parts for mixing (phr) Ingredients Ex. 1-5, Comp. Ex.1-4 Ex. 6 Acrylic polymer *1 100 100 Stearic acid 2 2 Anti-oxidant 2 2FEF Carbon black 55 55 Plasticizer 5 5 Diamine compound 0.5 — Guanidinecompound 2 — Imidazole compound — 1 Thiourea compound — 0.5 Quatenaryammonium salt — 0.3

TABLE 4 (Product names) Stearic acid: Runac S30 (Kao Corp.) Antioxidant:Naugard 445 (Uniroyal Chemical Company Inc.) FEF Carbon black: SeastSO(Tokai Carbon Co. Ltd.) Plasticizer: Adeka RS-735 (Asahi Denka Co.Ltd.) Diamine compound: Diak #1 (Dupont Dow Elastomers LLC) Guanidinecompound:Nocceler DT (Ouchi Shinko Chemical Industrial Co. Ltd.)Imidazole compound: SN-25 (Shikoku Chemicals) Thiourea compound:Nocceler TMU (Ouchi Shinko Chemical Industrial Co. Ltd) Quatenaryammonium salt: Katinal STB (Toho Chemical Industry Co. Ltd.)

1. A joining structure comprising: a heat-resistant hose; a member madeof aluminum or aluminum alloy; and an acrylic rubber compositioncomprising: monomer units of ethyl acrylate (A), n-butyl acrylate (B),and cure site monomer; and a ratio (B/A) of the amount of n-butylacrylate (B) with respect to ethyl acrylate (A) is 1.0 or less, whereinsaid acrylic rubber composition acts as a joining surface to join saidmember to said heat-resistant hose.
 2. The joining structure accordingto claim 1, wherein: said ratio B/A is from 0.1 to 1.0.
 3. The joiningstructure according to claim 1, wherein: said member made of aluminum oraluminum alloy is a hose connecting pipe, an intercooler, or an intakemanifold used in a turbocharger of an automobile.
 4. The joiningstructure according to claim 1, wherein: said acrylic rubber compositioncopolymerizes monomer units by emulsion polymerization, suspensionpolymerization, solution polymerization, or bulk polymerization.
 5. Thejoining structure according to claim 1, wherein: said acrylic rubbercomposition contains additional monomer units of at least one selectedfrom the group consisting of a compound containing carboxyl group, esteracrylate containing fluorine, ester acrylate containing hydroxyl group,ester acrylate containing tertiary amino group, methacrylate, alkylvinylketone, vinyl ether, allyl ether, vinyl aromatic compound, vinylnitrile, ethylene, propylene, vinyl chloride, vinylidene chloride, vinylfluoride, vinylidene fluoride, vinyl acetate, vinyl propionate, andalkyl fumarate.
 6. The joining structure according to claim 1, wherein:said cure site monomer is a cure site monomer containing carboxyl group,a cure site monomer containing epoxy group, or a cure site monomercontaining activated chlorine group.
 7. The joining structure accordingto claim 6, wherein: said cure site monomer containing carboxyl group ismonoalkyl ester maleate, monoalkyl ester fumarate, or monoalkyl esteritaconate.
 8. The joining structure according to claim 1, wherein: theamount of said cure site monomer in said acrylic rubber is 0.5-2% byweight.
 9. The joining structure according to claim 1, wherein: at leastone selected from the group consisting of a vulcanizing agent, carbonblack, anti-oxidant, plasticizer, processing aid, scorch retardant,flame retardant, and coloring agent are mixed into said acrylic rubbercomposition.
 10. (canceled)
 11. (canceled)
 12. (canceled)
 13. Thejoining structure according to claim 1, wherein: said heat-resistanthose is a single layer hose with a single rubber layer of said acrylicrubber composition.
 14. The joining structure according to claim 1,wherein: said heat-resistant hose is a multi-layer hose with aninnermost layer of said acrylic rubber composition and a middle or outerlayer of acrylic rubber or a rubber other than acrylic rubber.
 15. Thejoining structure according to claim 1, wherein: said heat-resistanthose having a reinforcement layer of reinforcement fiber or wires as amiddle layer or outermost layer thereof.
 16. The joining structureaccording to claim 1, wherein: said heat-resistant hose is used in ahigh heat-resistant hose of an air system or oil system of anautomobile.
 17. A heat resistant hose The joining structure according toclaim 16, wherein: said air system or oil system high heat-resistanthose is a supercharger hose, an engine oil cooler hose, an automatictransmission oil cooler hose, or a power steering hose.